Class: MysqlReplicator::Binlogs::RowsEventParser

Inherits:
Object
  • Object
show all
Defined in:
lib/mysql_replicator/binlogs/rows_event_parser.rb

Class Method Summary collapse

Class Method Details

.bit_set?(bitmap, index) ⇒ Boolean

Returns:

  • (Boolean) 


147
148
149
150
151
 
# File 'lib/mysql_replicator/binlogs/rows_event_parser.rb', line 147

def self.bit_set?(bitmap, index)
  byte_index = index / 8
  bit_index = index % 8
  (bitmap[byte_index] & (1 << bit_index)) != 0
end

.count_bits(bitmap, max_bits) ⇒ Object 



156
157
158
159
160
161
162
 
# File 'lib/mysql_replicator/binlogs/rows_event_parser.rb', line 156

def self.count_bits(bitmap, max_bits)
  count = 0
  max_bits.times do |i|
    count += 1 if bit_set?(bitmap, i)
  end
  count
end

.parse(event_type, payload, checksum_enabled, table_map) ⇒ Object 



34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
 
# File 'lib/mysql_replicator/binlogs/rows_event_parser.rb', line 34

def self.parse(event_type, payload, checksum_enabled, table_map)
  io = StringIO.new(payload)
  io.set_encoding(Encoding::BINARY)

  # 4bytes checksum at the end if CRC32 checksum is enabled
  payload_size = checksum_enabled ? payload.bytesize - 4 : payload.bytesize

  # Table ID (6 bytes)
  table_id = StringIOUtil.read_uint48(io)
  # Flags (2 bytes)
  flags = StringIOUtil.read_uint16(io)
  # Extra data length (2 bytes)
  extra_data_length = StringIOUtil.read_uint16(io)
  # Skip extra data if present
  io.read(extra_data_length - 2) if extra_data_length > 2

  # Column count (variable length encoded)
  column_count = read_packed_integer(io)

  # Columns present bitmap
  bitmap_size = (column_count + 7) / 8
  # A bitmap indicating which columns are present in the row data
  columns_present_bitmap = MysqlReplicator::StringIOUtil.read_array_from_int8(io, bitmap_size)
  # if UPDATE_ROWS event, after this bitmap, there is another bitmap for "columns present in the after image"
  columns_after_bitmap = event_type == :UPDATE_ROWS ? MysqlReplicator::StringIOUtil.read_array_from_int8(io, bitmap_size) : []

  # Parse row data
  table_def = table_map[table_id]
  rows = []
  while io.pos < payload_size
    if event_type == :UPDATE_ROWS
      before_row = parse_row(io, column_count, columns_present_bitmap, table_def)
      after_row = parse_row(io, column_count, columns_after_bitmap, table_def)
      rows << { before: before_row, after: after_row }
    else
      row = parse_row(io, column_count, columns_present_bitmap, table_def)
      rows << row
    end
  end

  {
    database: table_def[:database],
    table: table_def[:table],
    table_id: table_id,
    flags: flags,
    extra_data_length: extra_data_length,
    column_count: column_count,
    rows: rows
  }
end

.parse_row(io, column_count, columns_present_bitmap, table_def) ⇒ Object 



90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
 
# File 'lib/mysql_replicator/binlogs/rows_event_parser.rb', line 90

def self.parse_row(io, column_count, columns_present_bitmap, table_def)
  # Null bitmap
  # A bitmap indicating which columns are NULL
  present_count = count_bits(columns_present_bitmap, column_count)
  null_bitmap_size = (present_count + 7) / 8
  null_bitmap = MysqlReplicator::StringIOUtil.read_array_from_int8(io, null_bitmap_size)
  null_bit_index = 0

  row = []
  table_def[:columns].each_with_index do |column_def, column_index|
    unless bit_set?(columns_present_bitmap, column_index)
      next
    end

    column_name = column_def[:column_name]

    # Check if the column is NULL
    value = if bit_set?(null_bitmap, null_bit_index)
              nil
            else
              MysqlReplicator::Binlogs::ColumnParser.parse(io, column_def)
            end
    null_bit_index += 1

    row << {
      ordinal_position: column_def[:ordinal_position].to_i,
      data_type: column_def[:data_type],
      column_name: column_name,
      value: value,
      primary_key: column_def[:primary_key]
    }
  end

  row
end

.read_packed_integer(io) ⇒ Object 



128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
 
# File 'lib/mysql_replicator/binlogs/rows_event_parser.rb', line 128

def self.read_packed_integer(io)
  first = StringIOUtil.read_uint8(io)
  case first
  when 0..250
    first
  when 252
    StringIOUtil.read_uint16(io)
  when 253
    StringIOUtil.read_uint24(io)
  when 254
    StringIOUtil.read_uint64(io)
  else
    raise "Invalid packed integer: #{first}"
  end
end